For simplicity, I'm combining responses to the other posters in this thread into one reply:
1) Azelaic acid isn't an "androgen blocker". Dr. Lee has claimed that it works as a topical 5a-reductase inhibitor (lowering the conversion of testosterone into DHT), but there isn't any scientific evidence that it works that way in vivo.
2) "RU" is the common abbreviation on hairloss sites for RU58841, an experimental drug developed in 1994 by a French company. It may be the most effective topical antiandrogen (androgen receptor blocker) ever developed. It's not normally obtainable, except through some rather dodgy Chinese companies. It's expensive, and difficult to obtain.
3) There is no scientific evidence I'm aware of (other than a small experiment by an Israeli scientist, which I don't fully trust) that topical flutamide has any antiandrogenic effect where locally applied. To be sure, experiments with laboratory animals (hamsters, rats, and mice) have shown a general (systemic) antiandrogenic effect, but that's because of systemic absorption of the drug. There doesn't seem to be any local effect just where it's physically applied.